This application claims the priority of German Patent Application Serial No. 101 02 896.2, filed Jan. 23, 2001, the subject matter of which is incorporated herein by reference.
The present invention relates to a method of making an exhaust gas collector for multi-cylinder internal combustion engines.
Exhaust gas collector or manifolds are used in internal combustion engines to conduct exhausts produced during combustion in several cylinders in a cost-efficient single-flow system to an exhaust aftertreatment system, in particular to reduce emissions and noise levels. Unlike exhaust manifolds, which are made by a casting process, exhaust gas collectors, with or without integrated catalytic converter, are normally made of a many individual parts. Conventional exhaust manifolds or exhaust gas collectors, involved here, are, for example, described in German Pat. Nos. DE 195 10 602 C1 or DE 43 39 290 C2.
The individual parts are predominantly connected together by fusion welding. Disregarding here the typically very complicated air-gap insulated exhaust gas collectors, single-wall exhaust gas collectors are basically fabricated according to one of the following three principles of construction:
Half-shell construction
Tube construction
Combined shell-tube construction
The exhaust gas collector has a collector housing which interconnects a head flange, which is disposed on the multi-cylinder outlet side of a power engine, and an end flange for attachment, normally in single-flow configuration, of the discharging exhaust system. It is also generally known to accommodate components of the catalytic converter in the collector housing.
It would be desirable and advantageous to provide an improved method of making a high-quality exhaust gas collector in a cost-efficient manner for multi-cylinder internal combustion engines.
According to one variation of the present invention, a method of making an exhaust gas collector for multi-cylinder internal combustion engines, includes the steps of providing a tubular blank having a cross sectional dimension which corresponds to a diameter of a collector housing for an exhaust gas collector to be fabricated, and forming the blank into the collector housing with an inlet duct of substantially rectangular cross section with rounded narrow sides. Examples of suitable shaping processes include bending and press-forming or a compression process, to impart the inlet duct with a rectangular cross section having flattened long sides and rounded narrow sides. Subsequently, components of a catalytic converter can be installed in such an exhaust gas collector through the outlet side, and the outlet duct can then be shaped.
According to another variation of the present invention, a method of making an exhaust gas collector for multi-cylinder internal combustion engines, includes the steps of shaping a tubular blank by an internal high pressure forming process into a collector housing, and forming the collector housing with an inlet duct of substantially rectangular cross section with rounded narrow sides. In accordance with this variation, the collector housing is made on the basis a tubular blank through application of an internal high pressure forming process, whereby the inlet duct is produced on the inlet side by widening the initial or intermediate profile into a substantially rectangular cross section with rounded narrow sides. Thus, the inlet duct constitutes a single-piece component of the collector housing.
Both variations of the present invention allow manufacture of exhaust gas collectors which are comprised of a minimum of two components, namely the head flange and the collector housing with integrated outlet duct. It is not necessarily required to use a circular tube as blank in order to make an exhaust gas collector. Also, oval or polygonal profiles may be utilized. An exhaust gas collector according to the present invention can be made more cost-efficient because no welding operations are required, and also because the need for different tools is lessened in order to make the individual components. In particular, the absence of inhomogeneities, such as weld seams and overlaps, leads to an extended service life of an exhaust gas collector according to the present invention, which can be made for configurations with or without catalytic converter.
When integrating a catalytic converter in the collector housing, the collector housing is first formed with the inlet duct. Subsequently, the catalytic converter system, i.e., carrier and retaining mat, is fitted into the collector housing. This process is known in the art also as xe2x80x9ccanningxe2x80x9d. Then, the collector housing is subjected to a press-forming process to neck the outlet duct of substantially circular cross section in relation to the cross section of the collector housing.
Once the collector housing is produced, it is merely required to attach the head flange to the inlet duct. This may be realized through a welding operation.
Optionally, an end flange may be attached to the outlet duct. Depending on the size of the exhaust pipe, it is also possible to omit the provision of an end flange altogether. In this case, it is conceivable to form a bulbous portion on the end of the collector housing during press-forming of the outlet duct. A positive connection can then be implemented with the discharging exhaust pipe, for example, by means of a spring element.
According to another feature of the present invention, the inlet duct may be connected by a curved pipe section to the collector housing. This type of construction is space-saving and efficient.